Ceramic inserts for turning and milling
Oxide ceramics strengthened with Whisker SiC (S500, S400, S800). Good results in studies on the further performance development of ceramic tool materials were obtained by using admixture of high-strength whisker SiC (about 15- 30% weight) to the most Al2O3 ceramics with ZrO2 addition.
SiALON Silicon Aluminium Oxy-Nitride
It’s solid solution of aluminum oxide in the silicon nitride tetragonal structure. Chemical composition of the area enclosed by the formula:
SI6-ZALZOZN8-Z
where it fits from 0 to 4, this means that silicon nitride Si3N4 tetragonal structure of allotropic form is dissolved to 60% Al2O3
SiAlON Properties:
by maintaining the basic atomic bonds sialons have high mechanical properties similar to Si3N4
Properties similar to Si3N4, but:
– lower coefficient of thermal expansion
– greater resistance to thermal shock
Chemical properties are more similar to Al2O3
– More resistant to oxidation than Si3N4
For technical reasons, yttrium oxide Y2O3 and/or magnesium oxide MgO (called concentrator) is added to SiAlON, causing formation of glassy phase, which reduces the resistance to oxidation of SiALON Silicon Aluminium Oxy-Nitride.
SiALON Silicon Aluminium Oxy-Nitride.
In order to avoid the harmful effects of glassy phase after sintering, a controlled cooling should be carried out or heat treatment at 1400 ° C causing complicated reaction between glassy phase and SiAlON, leading to YAG (yttrium-aluminum garnet) compound support, witch provide high resistance to oxidation and creep.
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